Despite advances in computer science, there are many applications and tasks that are too complex or unstructured to be performed by unsupervised autonomous robots. Until machine intelligence is significantly improved, there will be a continuing need for direct human supervision and control for all but the simplest of tasks performed by robotic systems. Direct human control is made possible through the use of a teleoperator. A teleoperator is a general-purpose, remotely controlled, dexterous person-machine system. Teleoperators may be used to control devices in either a remote or virtual environment.
Often it is necessary to have a human operator physically removed from the actual work site, remotely operating and supervising the robot in the performance of difficult and dangerous tasks. Another application is virtual operation, in which a human can touch and/or manipulate objects in a virtual environment. Among these applications, medical simulation can allow users to explore anatomy and actually feel realistic representation of various tissues, perform virtual surgery or fly through arteries. Other virtual environment applications with force feedback include engineering, education, assisting disabled individuals, and entertainment.
In very simple systems the human operator is not provided with any sensory input from the remote manipulator other than the location of the manipulator relative to its environment (usually by the direct viewing of the operator when the manipulator arm is within view or via a camera when the manipulator is in a remote location). While visual observation may be enough sensory input for some tasks it often leaves the human operator feeling disconnected from the task because it provides the operator with a very low level telepresence. Telepresence is the quality of sensory feedback from a teleoperator to a human operator such that the operator feels present at the remote site.
An increased telepresence makes it possible for a human operator to undertake tasks which would be difficult or impossible with only visual feedback. Quality remote or virtual surgery, for example, would not be possible with only visual information being provided to the operator. In order to increase the operator's telepresence a haptic display is used to provide increased sensory feedback.
A haptic display generally includes several structural members connected at joints that permit relative movement of the members as the operator moves an associated control handle. As the operator moves the handle around a defined workspace, a control computer reads signals indicative of movements of each member and calculates the position of the handle relative to a defined reference. The computed information is then used to control the corresponding motion of a remote or virtual manipulator.
The forces and torque applied by the telemanipulator in a remote environment, or virtual manipulator in a virtual environment can be sensed or estimated by various techniques. A force/torque sensor may be mounted on the end-effector of the telemanipulator to directly measure the forces and torque encountered. In virtual environments, the virtual objects can be modeled as spring elements with a finite stiffness, and the forces and torque can be estimated by the intersection among the virtual objects.
The control computer transforms the measured or estimated forces and torque signals into appropriate output signals to control and reproduce a scaled representation of the forces and torque encountered in the remotes or virtual environment. The human operator thus appears to feel forces and torque exerted by the remote or virtual environment.